This invention concerns metal casting using sand molds.
Sand molds are made by placing a pattern in the cope and flask cavities of a mold machine, injecting sand into the cavities, and thereafter squeezing the sand to compress the sand into a finished mold by raising a lower squeeze plate relative to an upper fixed squeeze plate.
A riser is often provided in the upper half of the mold to allow molten metal to enter the riser, during casting, the metal contained within the riser maintained in a liquid state by an insulating or exothermic sleeve in the riser. The volume of metal in the riser makes up for shrinkage in the mold cavity. It is sometimes desirable to have an "open" riser which extends to the outside of the mold so that additional melt can be added from the outside as necessary.
An open riser has been difficult to form into the mold at the time the mold is made due to the nature of the sand mold making process when using an automatic mold making machine since sand could be dislodged, which could then drop into the main cavity.
Thus, a separate cutting operation has been required to provide an open riser.
U.S. Pat. No. 5,462,106 issued on Oct. 31, 1995 to the present inventor describes and claims a method which uses a heat consumable plug mated with a riser sleeve.
The plug is tapered and inserted into the riser tube as the sand is compressed. The plug prevents sand from entering the riser tube when sand is injected, and maintains a seal by the plug being driven into riser tube as the sand is compressed.
While successful, this approach requires a plug of a size matched to the diameter of the riser tube to be assembled into the riser tube each time a mold is made.
It is the object of the present invention to provide a method of making an open riser opening in a sand mold at the time the mold is made in an automatic mold making machine which does not require the assembly of a properly sized heat consumable plug into the riser sleeve each time a mold is constructed.